Di-alpha-naphthylzinc-titanium tetrachloride polymerization initiator and process



DI-ALPHA-NAPHTHYLZINC-TITANIUM TETRA- CHLORIDE POLYMERIZATION INITIATORAND PROCESS Willard C. Bull, Joplin, Mo., Joe H. Cain, Columbus, Kans.,Roland J. Spomer, Clinton, Ind., Herman L. Fiukbeiner, Jr., Pittsburg,Kans., and Robert W. Hill, Joplin, Mo., assignors to Spencer ChemicalCompany, a corporation of Missouri No Drawing. Application February20,1956 Serial No. 566,350

6 Claims. (Cl. 260-943) v This invention relates to new compositions ofmatter. More particularly, this invention is concerned with novelinitiators or activators for polymerizing olefins such as ethylene andpropylene. This invention is also concerned with novel processesofproducing such initiators. Ethylene has been polymerized heretofore athigh temperatures and very high pressures with the aid of initiators ofthe "free radical type. The polyethylenes resulting from high pressureprocesses have been suitable for some applications, but not for others.This is because it has been particularly difiicult to increase therigidity and softening points of high pressure polyethylenes to levelsnecessary for the desired applications. There has been some success inproducing polyethylenes with the desired properties by employing higherpressures. These processes, however, utilize pressures considered abovepractical limits for convenient and economical commercial production.Somewhat better results have been attained by utilizing lowertemperatures. However, the free radical initiators are not effective ininducing polymerization below rather high minimum reaction temperatures,below which it is desirable to effect polymerization. V e

. lnitiators of the .ionic type have been found to be somewhatsuccessful for the polymerization of ethylene and propylene at lowertemperatures and pressures. Among these may be mentioned such initiatorsas the alkali metal hydrides, Grignard reagents, triethyl aluminum andthe activated supported transitional elements. However, the products ofthese processes most often range from oils to low melting waxes. Inthose instances where a satisfactorily high molecular weight polymer isobtained, the process is accompanied by pressures in excess of 1000p.s.i.g., temperatures above 100 C., or reaction times in excess offifteen hours;

By means of the present invention an initiator is provided which willpolymerize polyethylene to high molecular weights at atmosphericpressures and room temperatures and is fiexibleas to pressure andtemperature in that it will proceed satisfactorily at high or very lowtemperatures and at high or low pressures.

' According to the present invention, it has been found that thecombination of di-alpha-naphthylzinc and titanium tetrachloride gives anew composition of matter which is an initiator of high activity for thepolymerization of ethylene and propylene. This is particularlysurprising since neither di-alpha-naphthylzinc nor'titaniumtetrachloride are elfective as polymerization initiators for olefinssuch as ethylene and propylene.

This novel initiator polymerizes ethylene and propylene at surprisinglylow temperatures and pressures to give products of high molecularweights and high softening points. It is, therefore, possible to formpolyethylene and polypropylene resins without resorting to the highertemperatures and pressures formerly used. A more suitable and convenientprocess employing mild conditions is accordingly also provided by thisinvention.

The initiator formed by contacting and reacting dialpha-naphthylzinc andtitanium tetrachloride is a novel composition that appears to be acomplex of presently undetermined composition which is insoluble in mostreaction media. Such complexes solvate with many media; however, thecomplex as well as solvated form thereof are useful initiators.

Di-alpha-naphthylzinc is very reactive but may be handled convenientlyout of contact with air and water.

The initiator is conveniently prepared by intimatelymixingdi-alpha-naphthylzinc and titanium tetrachloride in a liquid medium. Itis preferred to employ as the medium an inert organic solvent such as asaturated aliphatic or alicyclic hydrocarbon, an aromatic hydrocar bonor halogenated derivates of such hydrocarbons. Preferred organic mediaare pentane, hexane, cyclohexane, isooctane, petroleum ether, benzene,toluene, monochlorobenzene and the like, and mixtures thereof.

To prepare the initiator, a ratio of about one molar equivalent ofdi-alpha-naphthylzinc to 0.25 to 4.00 molar equivalents of titaniumtetrachloride may be used. The preferred initiator comprises a ratio ofabout one mole of di-alpha-naphthylzinc combined with about one mole oftitanium tetrachloride.

The order in which the reactants are added to the medium is generallynot critical. However, in certain situations it appears that solvationoccurs between the medium and one of the reactants which lowers itsreactivity. Therefore, the order of addition of the reactants should beadjusted appropriately.

After di-alpha-naphthylzinc and titanium tetrachloride have been united,reaction takes place at room temperature although lower and highertemperatures may be used.

The initiator provided by this invention is particularly useful in thepolymerization of ethylene and propylene since it inducespolymerization, surprisingly, at relatively low temperatures andpressures and gives products of high molecular weight and high softeningpoints. For best results, it is preferred to use the initiator soonafter preparation, vizl, within an hour after preparation.

As previously indicated above, polymerization of ethylene and propyleneis eflected with the initiator at low temperatures and pressures. Thepolymerization may be conveniently effected with the initiator attemperatures as low as that of liquid nitrogen and as high as thedecomposition temperature of the initiator which is about 300-5 00 C.However, excellent results may be attained with convenience at about 0C. to about C. and preferably at 20 C. to 60 C. The higher temperaturesapparently increase the rate of polymerization although the polymers soproduced may be of relatively lower molecular weight than those obtainedat lower temperatures.

Polymerization is achieved in this process with the described initiatorover a wide pressure range from subatmospheric pressures to pressures ofabout 1000 p.s.i.g. and higher, such as pressures of 2000 atmospheres.However, low pressures from about atmospheric to about 200 p.s.i.g. givegenerally preferred results and are most economically used. In general,the polymerization rate is increased by the higher pressures. However,the activity of the initiator is such that there is not much reason inoperating at the higher pressures.

To effect the polymerization, the ethylene and/or propylene arecontacted with the initiator, preferably under liquid reactionconditions although vapor phase operations are within the scopecontemplated by this invention. Inert organic solvents such as saturatedaliphatic or alicyclic hydrocarbons, aromatic hydrocarbons orhalogenated derivatives of such hydrocarbons may be used as the reactionmedium. Preferred organic media are pentane, hexane, cyclohexane,isooctane, petroleum ether, benzene, toluene, monochlorobenzene and thelike and mixtures thereof. In addition, by proper selection oftemperatures and pressures liquid ethylene and/ or propylene also may beused as the medium.

The amount of initiator used to effect polymerization of ethylene andpropylene is not critical; all that is required is that an effectiveamount be used. The rate of polymerization as well as the molecularweight of the polymers can be varied by changing the ratio of initiatorto ethylene and propylene. Some loss of activity of the initiator may beexpected due to the presence of impurities that may be present in thereaction. It is, therefore, desirable to employ more than what may beconsidered to be trace amounts of the initiator.

The relationship of initiator to reaction medium is subject to widevariation. The larger amounts of initiator give a more rapidpolymerization than do lesser, minimum amounts. However, as little as.002 mole of initiator per 100 ml. of medium elfect polymerization.

By the use of the described initiator, it has been found that highlypure ethylene and propylene need not be used to achieve satisfactorypolymerization. Ethylene and propylene of 95% purity containing loweralkanes, nitrogen, hydrogen and other inert materials are entirelysatisfactory at the low temperature-low pressure conditions which may beused with the initiator. This is opposite to conventional high pressureprocesses wherein high purity ethylene must be employed. The systemshould be maintained substantially free of water and oxygen, however,since these substances appear to affect the initiator adversely.

The rate of reaction is, of course, dependent on the other processconditions as already stated. The initiator is of such exceptionalactivity, however, that at 50 C. and 50 p.s.i.g. good yields ofpolyethylene and polypropylene result in a matter of minutes.

By carefully controlling the operating conditions, polymers may beproduced having a wide range of molecular Weights. Under the preferredconditions, viz., low temperature and low pressure, the polymerizationusing the initiator of this invention gives products averaging about30,000 molecular weight or greater. Products much higher, such as100,000, are also produced. Such polymers have softening pointsgenerally in excess of 120 C. (Vicat) and are substantially more rigidthan polymers produced by conventional commercial high pressureprocesses. The polymers are free of zinc and contain only occasionalinsignificant traces of titanium.

The following example is added to illustrate working embodiments of theinvention, it being understood that the invention is not to be therebylimited to this example.

Example 1 A solution of di-alpha-naphthylzinc was made from .042 mole ofdi-alpha-naphthylmercury and .075 mole zinc dust in 75 ml. decalin andthe mixture refluxed for six days. The reaction mixture was then cooledand filtered. The solid material so obtained included a metallic residueand also a large amount of a yellowish crystalline solid which reactedviolently with methanol. A portion of this material was quicklytransferred to 100 ml. of hexane. The yellow crystals dissolved onlypartially in the hexane. Then 0.5 ml. titanium tetrachloride was addedto the hexane suspension. An immediate reaction produced a suspension ofa dark solid in a clear red solution.

The initiator in the hexane suspension was added to a Parr autoclave at25 C. and ethylene added at 50 p.s.i.g. to the agitated mixture. Thetemperature was not controlled. In 45 minutes reaction 5.9 gm. ofpolyethylene formed. It had a molecular weight of 105,000 and a Vicatsoftening point of 123 C.

Various changes and modifications of the invention can be made and tothe extent that such variations incorporate the spirit of thisinvention, they are intended to be included within the scope of theappended claims.

What is claimed is:

1. A polymerization initiator formed by reacting a ratio of about onemole of di-alpha-naphthylzinc with 0.25 to 4 moles of titaniumtetrachloride in the presence of an inert organic solvent.

2. The process which comprises reacting a ratio of about one mole ofdi-alpha-naphthylzinc with 0.25 to 4 moles of titanium tetrachloride inan inert medium toproduce a reaction product.

3. The process which comprises reacting a ratio of about one mole ofdi-alpha-naphthylzinc with 0.25 to 4 moles of titanium tetrachloride inthe presence of an inert organic solvent to produce a reaction product.

4. The process which comprises contacting a l-olefln of less than 4carbons with a polymerization initiator consisting essentially of thereaction product of a ratio of about one mole of di-alpha-naphthylzincwith 0.25 to 4 moles of titanium tetrachloride in the presence of aninert liquid medium at a temperature from 0 C. to 300 C. and a pressurefrom atmospheric to 2000 atmospheres to produce a polymer of the olefin.

5. The process that comprises contacting a l-olefin of less than 4carbons with a polymerization initiator consisting essentially of thereaction product of a ratio of about one mole of di-alpha-naphthylzincwith 0.25 to 4 moles of titanium tetrachloride in the presence of aninert organic solvent at a temperature from 0 C. to C. and a pressurefrom atmosphere to 1000 p.s.i.g. to produce a polymer of the olefin.

6. The process that comprises contacting a l-olefin of less than 4carbons with a polymerization initiator consisting essentially of thereaction product of a ratio of about one mole of di-alpha-naphthylzincwith 0.25 to 4 moles of titanium tetrachloride in the presencev of aninert organic solvent at a temperature from 0 C. to 100 C. and apressure from atmospheric to 200 p.s.i.g. to produce a polymer of theolefin.

References Cited in the file of this patent UNITED STATES PATENTS2,475,520 Roedel July 5, 1949 2,721,189 Anderson et al Oct. 18, 19552,762,791 Pease et al. Sept. 11, 1956, 2,816,883 Larcher et al. Dec. 17,1957 FOREIGN PATENTS 534,792 Belgium Jan. 31, 1955 533,362 Belgium May16, 1955 OTHER REFERENCES Gilman et al.: 3'. Organic Chem, 10, 505-515,November 1945,

4. THE PROCESS WHICH COMPRISES CONTACTING A 1-OLEFIN OF LESS THAN 4CARBONS WITH A POLYMERIZATION INTIATOR CONSISTING ESSENTIALLY OF THEREACTION PRODUCT OF A RATIO OF ABOUT ONE MOLE OF DI-ALPHA-NAPHTHYLIZINCWITH 0.25 TO 4 MOLES OF TITANIUM TETRACHLORIDE IN THE PRESENCE OF ANINERT LIQUID MEDIUM AT A TEMPERATURE FROM 0*C, TO 300* C., AND APRESSURE FROM ATMOSPHERIC TO 2000 ATMOSPHERES TO PRODUCE A POLYMER OFTHE OLEFIN.